Wis. Stat. § 938.263: Amendment of petition.

(1) To cure defect. Except as provided in s. 938.255 (3), no petition, process or other proceeding may be dismissed or reversed for any error or mistake if the case and the identity of the juvenile named in the petition may be readily understood by the court; and the court may order an amendment curing the defects.

(2) Before or after plea. With reasonable notification to the interested parties and prior to the taking of a plea under s. 938.30, the petition may be amended at the discretion of the court or person who filed the petition. After the taking of a plea, the court may allow amendment of the petition to conform to the proof if the amendment is not prejudicial to the juvenile.